1. Technical Field
The present invention relates generally to a location measurement apparatus and method and, more particularly an apparatus and method that classify irregular communication RSSIs into three levels using two sensing nodes in a defense sensor network environment having limited resources and more accurately measure the location of an object for each of the levels.
2. Description of the Related Art
Location information is a fundamental element that enables a user or an object to recognize a surrounding environment, and thus is a core element in ubiquitous computing. Therefore, a sensor network-based location recognition technique is attracting attention as a sensor network-related key element technology in a ubiquitous defense (“U-defense”) environment.
However, existing studies are intended to calculate and track a location using only one or more close nodes within a communication range in an environment in which a sufficient number of sensor nodes have been provided. In particular, if the number of nodes participating in location measurement in a resource-limited defense sensor network environment is not sufficient, the accuracy of the tracking of the location may be very low or the tracking of the location may be impossible. Accordingly, the accuracy of the tracking of the location must be ensured using a surrounding environment.
Methods of measuring the location of an object may be classified into a range-based method and a range-free method.
The range-based method is a method of estimating a range value using an ultrasonic sensor or a received signal strength indication (RSSI) device and then calculating a location based on the estimated range value. In particular, the method of measuring a location using the RSSI device is suitable for a resource-limited sensor node. However, such an RSSI device involves (non-negligible) errors because of problems such as multi-path fading.
Meanwhile, the range-free method is a method of approximately measuring the location of an object based on whether or not communication between sensor nodes is possible without using any alternative device. However, when the density of the sensor nodes is low, the range-based method that calculates a location based on a range value using a small number of sensor nodes may be more effective than the range-free method.
Accordingly, the range-based method and the range-free method have their own advantages/disadvantages in the measurement of the location of an object in defense sensor network environments. In other words, a novel method for improving the accuracy of the calculation of a location by integrating the advantages of the range-based method and the range-free methods described above is still required.
The conventional location measurement method calculates a location generally using only one or more close nodes within a communication range. However, if there are a smaller number of nodes participating in the calculation of a location in a resource-limited defense sensor network environment, in particular in a sensor network environment with a low density, the accuracy of the calculation of a location may be very low or the calculation of a location may be impossible.